Abstract: Zhejiang province issued the 《Discharge standard of major water pollutants for municipal wastewater treatment plant》(hereinafter referred to as Zhejiang standard),which has beeneffected since January 1,2019.The standard stipulates the control of COD_Cr,ammonia nitrogen,total nitrogen and total phosphorus. Zhejiang standard reconstruction project, Chuojiang sewage treatment plant of Yiwu,kept the existing sewage treatment scale of 150000 m³/d unchanged,and the effluent quality standard would be upgraded from grade A standard to Zhejiang standard. According to the analysis of the actual operation situation,on the basis of the original treatment system,the removal of total nitrogen and total phosphorus would be mainly strengthened. Through the transformation and optimization of some valves and pumps,process instruments such as ORP,ammonia nitrogen and nitrate nitrogen meter were added,and the carbon source dosing system and phosphorus removal dosing system were added as well,so as to improve the process control and effluent stability,and the effluent could stably meet the Zhejiang standard,The project could provide some reference for retrofitting similar wastewater treatment projects.